It is during this state withdrawn forcibly backwards over the glans, and in this situation, while being itself the first cause of constriction, it induces another -- namely, an arrest to the venous circulation, which is followed by a turgescence of the glans.

Considering all these facts, we must regard the fall of arterial pressure, the depression of the fontanelle, and the turgescence of the vessels of the limbs as phenomena concomitant with bodily rest and warmth, and we have no more right to assign the causation of sleep to cerebral anæmia than to any other alteration in the functions of the body, such as occur during sleep.

But even if we confine ourselves to the genital region, while in man that portion of the penis which enters the vagina, and especially the glans, is normally the only portion which, even during turgescence, is sensitive to voluptuous contacts, in woman the whole of the region comprised within the larger lips, including even the anus and internally the vagina and the vaginal portion of the womb, [89] become sensitive to voluptuous contacts.

In the anthropoid apes, as the gorilla, the large clitoris and the nymphæ become prominent in sexual excitement, but the less development of the clitoris in women, together with the specifically human evolution of the mons veneris and larger lips, renders this sexual turgescence practically invisible, though it is perceptible to touch in an increased degree of spongy and elastic tension.

Kissing and the privilege of sleeping with the friend are, however, sought, and at such times it often happens that even the comparatively unresponsive friend feels more or less definite sexual emotion (pudendal turgescence, with secretion of mucus and involuntary twitching of the neighboring muscles), though little or no attention may be paid to this phenomenon, and in the common ignorance of girls concerning sex matters it may not be understood.